My mother works with elderly drug addicts[1], and all whom's met moved to the city as young adults, either in search of drugs or having fallen into the drug culture. I don't think she's encountered any veterans, but San Francisco has certainly been a drug haven since the 1960s, the drug culture has destroyed countless lives, and no doubt there are plenty of veterans among that cohort.

Have things gotten worse, recently? The addict population definitely has grown over the past 20 years; even the older addicts will tell you that. But the city has also greatly gentrified over that time and has seen significant demographic shifts, including decreases in communities which historically saw most of the violent crime. There are plenty of statistics to throw around to support whatever claim you want.

[1] She works for IHSS, a combined Federal and State program that provides elderly requiring living assistance (e.g. cleaning, grocery shopping, accompanying on medical appointments, etc) with an allowance to pay care workers--it works both as assistance for poorer elderly, and as a work program for everybody else. There are IHSS-like programs across the country. But in San Francisco the vast majority of people receiving IHSS allowances seem to be former or often current drug users. I think she's only had one client who wasn't an addict.